Electronic controlled fuel supply system for high pressure injector

ABSTRACT

An electronically controlled fuel supply system is provided for employing a plurality of fuel injectors which maximize SAC pressures under both low speed and high speed operating conditions and are capable of sustaining SAC pressures in excess of 30,000 psi. The fuel supply system of the present invention includes a gear pump which supplies pressure-modulated fuel to a fueling channel and to a timing channel and from there to a plurality of injectors. Fuel pressure regulator means and timing fluid pressure regulator means are provided in the fueling and timing channel, respectively. An electronic control unit receives information relating to engine operating conditions from a plurality of sensors and actuates the fuel pressure regulator means and the timing fluid pressure regulator means to adjust the pressure as required for the specific engine operating conditions. The timing fluid is delivered to the injectors by the present system at a pressure sufficient to sustain a hydraulic link within the injector of the length necessary to maintain high SAC pressures during injection. Several embodiments of a fuel supply system which achieves these objectives are disclosed. A mounting integral with the cylinder head for an electronically controlled injector fuel supply system is also provided.

TECHNICAL FIELD

The present invention relates generally to fuel supply systems forsupplying fuel to the fuel injectors on an internal combustion engineand particularly to an electronically controlled fuel supply systemcapable of meeting the fuel supply requirements of high pressure fuelinjectors.

BACKGROUND ART

In the quest for high efficiency emissions-free internal combustionengines, engine manufacturers have attempted to develop engine fuelsupply systems that achieve complete fuel combustion. While this goalhas thus far proved somewhat illusory, significant improvements in bothcombustion efficiency and emissions reduction have occurred. Simple,reliable engine fuel systems of reasonable cost which will achieve theaforesaid goals are still being sought, however.

A major purpose in seeking complete fuel combustion is to reducepolluting engine emissions, especially in the levels of hydrocarbons,nitrogen oxides and particulate materials. Fuel injectors, inparticular, have been designed purporting to achieve efficiency ofcombustion, fuel economy and emissions abatement. Injectors such asthose described in U.S. Pat. Nos. 3,951,117, 4,463,901, and 4,621,605,assigned to the same assignee as the present invention, have proven tobe effective, reliable and economical. However, the achievement ofproposed further restrictions on levels of hydrocarbons, nitrogen oxidesand particulates in vehicle emissions could present problems, even withinjectors such as these. The cost effectiveness and fuel economyassociated with currently available fuel injectors is likely to besacrificed, especially if after treatments such as catalysts arerequired to achieve acceptable levels of these pollutants. Not only canafter treatments be costly, they also can present substantialmaintenance problems.

Therefore, dealing with pollutants at the source--in the combustionspace--presents a simpler, more efficient, cost effective solution. Thismeans increasing the efficiency of the combustion process which, inturn, requires the injection of fuel at high pressures, considerablyhigher pressures than have heretofore been attained, particularly duringlow speed engine operation. The injection pressure capabilities ofpreviously available fuel injectors has been limited to SAC pressures(pressure of the fuel in the injection chamber just in front of theinjector spray holes) to under 20,000 psi.

In order for each of the engine injectors to be able to sustain SACpressures substantially above 20,000 psi, however, the engine fuelsupply system must be able to provide precisely controlled amounts offuel and timing fluid to each injector at the precise time required inthe injection cycle. The fuel supply systems described in U.S. Pat. Nos.3,951,117; 4,463,901 and 4,621,605 are designed to supply fuel andtiming fluid to injectors in which SAC pressures are limited to lessthan 20,000 psi, even under high speed engine operating conditions.While these fuel supply systems adequately meet the needs of such fuelinjectors, they are not sufficiently responsive to engine operatingconditions to supply the needs of very high pressure injectors.Moreover, these fuel supply systems are not designed to cooperate withfuel injectors that must pressurize the fuel to a substantial level inthe low speed operating range without increasing the injection pressuremore than necessary in the high speed operation range. Further, they arenot sufficiently sensitive to the wide range of engine operatingparameters required for the efficient operation of high pressureinjectors, nor do they provide the degree of precise independent controlof timing pressures needed.

Many of the fuel supply systems currently available, moreover, are madeup of components such as pumps, pressure regulators and fuel lines thatare mounted externally of the engine head thereby increasing the risk offuel leakage, and further complicating maintenance and other problemsassociated with fuel plumbing external to the engine head.

Consequently, there is a need for a fuel supply system capable ofresponding precisely to a wide range of engine operating parameters toprovide the precise supply of both fuel and timing fluid to each enginefuel injector required to enable each injector to achieve SAC pressuresin excess of 30,000 psi during injection. There is a further need forsuch a fuel supply system including components that may be integrallymounted with the engine cylinder head in locations that will enhance theefficient operation of these components.

DISCLOSURE OF THE INVENTION

It is a primary object of the present invention, therefore, to overcomethe disadvantages of the prior art and to provide a fuel supply systemcapable of the precision of response to engine operating conditionsrequired to supply the precise amounts of fuel and timing fluid to theengine fuel injectors while also achieving SAC pressures in excess of30,000 psi.

It is another object of the present invention to provide a fuel supplysystem for fuel injectors capable of achieving high SAC pressures thatis electronically controlled.

It is yet another object of the present invention to provide anelectronically controlled fuel supply system for high SAC pressure fuelinjectors that supplies the precise quantity of fuel and timing fluidrequired to achieve pressurization of the fuel in the injector to asubstantial level in low speed operating ranges without undesirablyelevating injection pressures in the high speed operating ranges.

It is a further object of the present invention to provide anelectronically controlled fuel supply system for use with open nozzletype high pressure fuel injectors wherein the components of the systemare integrally mounted with the engine head to supply fuel and timingfluid to a plurality of such injectors associated with a common fuelrail and a common timing fluid rail located internally of the enginehead.

It is a still further object of the present invention to provide anelectronically controlled fuel supply system responsive to throttleposition and other engine operating parameters to control the pressureof the timing fluid by an electronically actuated pressure controller.

It is still another object of the present invention to provide anelectronically controlled fuel supply system for high pressure fuelinjectors wherein the quantity of timing fluid metered into eachinjector is electronically controlled in response to pressure(P-metered) or pressure-time (P/T-metered) or a combination of bothpressure and pressure-time considerations.

In accordance with the aforesaid objects, an electronically controlledfuel supply system capable of meeting the fuel and timing fluid supplyrequirements for fuel injectors that achieve pressures in the injectionchamber in excess of 30,000 psi is provided. The system includescompletely independent fueling and timing channels, each of which isconnected to a plurality of high pressure injectors. Control of thequantity of fuel to be injected is achieved through the fueling channelin accordance with pressure-time (PT) principles. Control of thequantity of fuel metered into the injector timing chamber is achievedthrough the injection timing channel according to pressure (P)principles, pressure-time (PT) principles, or both. Electronic controlmeans responsive to throttle position and various engine operatingparameters monitors the pressure of both the fuel in the fueling channeland the fuel in the injection timing channel and actuates pressurecontrol means to adjust the fuel pressure and the timing fluid pressureas required to achieve the desired quantity and the correct timing ofinjection for the condition of the engine. The present inventionadditionally provides several embodiments of control means for achievingefficient control of the timing fluid pressure so that a hydraulic linkof a length needed to control the timing of injection of fuel at SACpressure in excess of 30,000 psi is produced in the injectors. Amounting arrangement wherein the various components of the presentsystem may be mounted in separate locations integrally with the enginecylinder head is also provided.

Further objects and advantages will be apparent to one skilled in theart from the following description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a high pressure fuelinjector;

FIG. 2 is a graphic representation of the timing pressure requirementsfor the fuel injector of FIG. 1, wherein the timing fluid is P-meteredat low speeds and PT-metered at higher speeds;

FIG. 3 is a graphic representation of the fueling pressure requirementsof the fuel injector of FIG. 1 at different engine speeds;

FIG. 4 is a graphic representation of the timing pressure requirementsof the fuel injector of FIG. 1, wherein the timing fluid is P-metered atall speeds;

FIG. 5 is a schematic diagram of one embodiment of a fuel supply systemaccording to the present invention;

FIG. 6 is a schematic diagram of a second embodiment of a fuel supplysystem according to the present invention;

FIG. 7 is a schematic diagram of a third embodiment of a fuel supplysystem according to the present invention;

FIG. 8 is a schematic diagram of a fourth embodiment of the presentinvention;

FIG. 9 is a schematic diagram of a fifth embodiment of the presentinvention;

FIG. 10 is a top view of an engine cylinder head showing the fuel supplysystem of the present invention mounted in place;

FIG. 11, is a side view of the engine cylinder head of FIG. 10; and

FIG. 12 is a cross-sectional view of an engine cylinder head taken alonglines 12--12 of FIG. 11.

Best Mode for Carrying Out the Invention

High pressure fuel injectors of the type described in U.S. Pat. No.4,721,247, assigned to the same assignee as the present invention,require careful and precise metering of both the fuel and the timingfluid supplied to the injector to achieve the efficiency of combustionand resultant excellent emissions abatement characteristic of theseinjectors. The fuel demands of the high pressure injector are similar tothose of any other PT-metered injector. That is, the amount of fuelactually metered is a function of the supply pressure and the totalmetering time the fuel flows into the injector. Control of the timingfluid, however, must not only be completely independent from the controlof the fueling, but must also be infinitely variable to achieve thevariable timing which is necessary to take advantage of the high SACpressures produced by this kind of high pressure injector. The presentinvention proposes several embodiments of fuel and timing fluid controlmeans to be employed in an electronically controlled fuel system for thehigh pressure injector described herein.

Referring to the drawings, FIG. 1 illustrates one type of high pressurefuel injector the present fuel supply system is intended to supply. Thisand other similar high pressure fuel injectors are described in commonlyowned U.S. Pat. No. 4,721,247, the disclosure of which is herebyincorporated by reference. The fuel injector 10 of FIG. 1 is of the opennozzle type and typically reaches SAC pressures in excess of 35,000 psiduring engine operation. Fuel injector 10 is received, in a conventionalmanner, in the head of an internal combustion engine (not shown).

The body of the fuel injector 10 is formed of two sections, an injectorbarrel 12 and a one-piece injector cup 14. Extending axially through thefuel injector is a bore 16 within which is disposed a reciprocatingplunger assembly 18. The reciprocating plunger assembly 18 is comprisedof three serially arranged plungers: an injection plunger 20, anintermediate plunger 22, and an upper plunger 24. A compensating chamber26 is formed below the intermediate plunger 22 and includes disposedtherein a coil spring 28 which receives the upper end 21 of injectionplunger 20 and engages an actuating member 30 located at the upper end21 of plunger 20. The lower end of spring 28 rests upon a seat 32 formedin the injector cup 14 so that the force of the spring 28 exerted on theactuator 30 will draw the injection plunger upwardly into engagementwith the intermediate plunger 22 to force the three plunger elementstogether from completion of an injection cycle up until metering andtiming has started for the next injection cycle.

The upper end of a plunger return spring 34 engages the uppermost end(not shown) of upper plunger 24, while the lower end of return spring 34is seated against the top 36 of the injector barrel 12. Return spring 34biases the upper plunger 24 upwardly to engage a cam operated actuator(not shown) to uncover a timing fluid fill passage 38, thereby allowingthe timing fluid to enter passage 38 as indicated with sufficientpressure to separate the intermediate plunger 22 from the upper plunger24 as shown at 40 by compressing the spring 28. The extent of theseparation between the upper plunger 24 and the intermediate plunger 22is determined by the equilibrium between the spring force 28 and theforce produced by the pressure of the timing fluid acting on the area ofintermediate plunger 22. The greater the separation between plungers 22and 24, the greater the advance of injection timing.

Simultaneously with the flow of timing fluid into passage 38, fuel forinjection is metered through a fuel supply passage 42 into the injectorcup 14. Fuel then flows into a fuel channel 44 located in the injectorcup circumferentially about lower plunger 20 and into an injectionchamber 46. The injection orifices (not individually illustrated) arelocated at the lowermost end of chamber 46 in nozzle 48. During themetering of injection fuel, the injection chamber 46 will be partiallyfilled with a precisely metered quantity of fuel in accordance with theknown "pressure/time" (PT) principle, wherein the amount of fuelactually metered is a function of the fuel supply pressure and the totalmetering time that fuel flows through the orifice in fuel passage 42into the injector. This orifice (not shown) in passage 42 has carefullycontrolled hydraulic characteristics which achieve the desiredpressure/time fuel metering capability. The position of the plungerassembly 18 in FIG. 1 is shown in the position it occupies during themetering of both the fueling and timing portion of the injection cycle.

During injection, the upper plunger 24 is driven downward by a cam (notshown), which forces timing fluid out of space 40 and through passage 38until the plunger 24 blocks passage 38. Timing fluid is trapped in thespace 40 between the upper plunger 24 and the intermediate plunger 22,thus forming a hydraulic link which causes all three plungers to move inunison toward the nozzle 48. The movement of the lower plunger 20 intofuel-containing injection chamber 46 will result in the pressurizationof this fuel once the plunger 20 has moved far enough into chamber 46 tofill that part of the chamber not otherwise filled with fuel. Thedistance point from the end of nozzle 48 to where injection is startedis termed the "solid fuel height" and determines the point in theplunger's travel when injection actually begins. The solid fuel heightin a high pressure injector is achieved when the plunger edge 53 is at apoint significantly below the fuel passage 42, which enables high SACpressures to be achieved.

The three plunger assembly 18 of the fuel injector of FIG. 1 transmitsforce for the injection of the fuel from the upper plunger 24 throughthe hydraulic link at 40 to the intermediate plunger 22 and finally tolower plunger 20 so that, in effect, the force of the plunger assemblyacting upon the timing fluid is co-equal to that acting upon the fuel tobe injected. However, because the lower plunger 20 has a significantlysmaller diameter than the intermediate and upper plungers (22, 24), thepressure to which the timing fluid is subjected can be much lower and,therefore, more easily sustained than the pressure to which the fuel inchamber 46 is subjected. The large diameter of plunger 22 associatedwith a lower timing fluid pressure also permits a large return springand thus a large return force to be applied.

At the end of injection the hydraulic link at 40 is collapsed, andtiming fluid is forced out of the injector through a drain passage 50.When all of the timing fluid has been drained, upper plunger 24 andintermediate plunger 22 are no longer separated, but are in mechanicalcontact. During this stage in the injection cycle, any fuel enteringpassage 42 will be directed out of the injector through drain 52.

In order to achieve precise control over the timing of injection, thusassuring the efficiency of combustion timing fluid having a variablepressure is supplied for establishing a hydraulic link of a length asrequired to vary the time at which the plunger assembly reaches thesolid fuel height. Consequently, precise control of the pressure of thetiming fluid supplied to the injector through passage 38 is required.Since the timing fluid typically used in fuel injectors is fuel, thepresent invention provides a timing fluid supply system for highpressure injectors which is an integral part of, yet is controlledindependently from, the injector fuel supply.

The electronically controlled fuel supply system of the presentinvention, therefore, includes a dual channel fuel supply, one channelprovides fuel for injection to the injector through passage 42, and theother channel provides fuel to the injector through passage 38 to beused as timing fluid. The fueling channel controls the quantity of fuelto be injected in accordance with PT (pressure/time) metering through anorifice in passage 42 in the injector. FIG. 2 illustrates, in graphicform, the pressure requirements for a high pressure injector which isP-metered at low speeds and PT-metered at higher speeds for variousinjected quantities of fuel. FIG. 3 illustrates, in graphic form.,typical pressure requirements for a range of injected fuel quantities atengine speeds from 1000 to 5000 rpm.

The injection timing channel controls the quantity of fuel metered intothe timing passage 38 of the injector to create the hydraulic link at 40(FIG. 1). The length of the hydraulic link may be controlled by thepressure acting against the spring 28, in which case it is P-metered.Alternatively, the length of the hydraulic link at 40 may be PT-meteredand controlled by the size of the orifice in passage 38 and the lengthof time during which timing fluid is allowed to be metered into thetiming fluid chamber, or the length of the hydraulic link may be bothP-metered and PT-metered. FIG. 4 illustrates, in graphic form, thetiming supply pressures required to produce plunger separations and,therefore, hydraulic links of various lengths for an engine that isP-metered at all speeds.

FIGS. 5-9 illustrate, in schematic form, different embodiments ofelectronically controlled fuel supply systems that may be employed inconjunction with the high pressure injector of FIG. 1. Each of theseproposed fuel supply systems will supply fuel and timing fluid in theamounts and at the pressures required to establish a variable lengthhydraulic link sufficient to advance timing in a manner consistent withengine conditions. Although the present fuel supply system is describedprimarily with reference to a single high pressure fuel injector, thesystem is intended to meet the fuel and timing fluid supply requirementsof a plurality of such fuel injectors, the exact number of fuelinjectors being dependent on the particular engine.

The electronic controls for the injector fuel and timing fluid supplysystem described herein may be provided by an electronic control unit asdescribed below in connection with the several embodiments of thepresent invention. An electronic control unit suitable for this purposewill preferably include some type of microprocessor (not shown) capableof receiving electrical control inputs from, for example, pressuretransducers. Additional control inputs can be provided by othertransducers, such as throttle transducers, by sensors, such as amagnetic speed sensor, and the like. Appropriate connections must beprovided between the sources of control input and the microprocessor.The control input information is processed by the microprocessor andsignals responsive to this information are generated by themicroprocessor to actuate the various pressure controlling components ofthe present system. Since the objective to be achieved herein is theprecise control of the pressure of both fuel and timing fluid suppliedto the injector, control inputs from a large number of engine operatingconditions are directed to a microprocessor. The microprocessor thenprocesses this information and transmits signals to actuate pressureregulating means to adjust the pressure of fuel and timing fluid inaccordance with the control inputs.

FIG. 5 illustrates a basic closed loop electronically controlledinjector fuel supply system according to the present invention. Thisembodiment includes a source of fuel 68, and a gear pump 70 with apressure regulator 72 upstream of two rotary throttle valves 74, 76.Throttle valve 74 is located in the injection timing fluid channel 78,and throttle valve 76 is located in the fueling channel 80. A pressuretransducer 82 downstream of throttle valve 74 measures the pressure ofthe timing fluid/fuel in channel 78, while a similar pressure transducer84 measures the pressure of the fuel in channel 80. These pressuremeasurements are transmitted to an electronic control unit 86 (ECU).This electronic control unit, in its most basic form, requires only anengine throttle position 88 signal and an engine speed (RPM) 90 signalas input to control the pressure of the fuel in channels 78 and 80. Alook up table (not shown) is included in ECU 86. The desired fuel andtiming fluid pressures for specific engine throttle positions and enginespeeds are programmed into a look up table so that when the ECU receivespressure information from the pressure transducers 82, 84, this pressureinformation is compared with the desired pressures for the specificengine throttle position and engine RPM and the ECU transmits signals tothe throttle valves 74, 76 to set them accordingly. The position of thethrottle valve 74 will control the amount of timing fluid supplied tothe injector and, therefore, the pressure of the timing fluid and theadvance of timing. Because this system includes a feedback signalindicative of the pressure produced by the control signal, it isreferred to as a closed loop control.

Although only a throttle position signal and an engine speed (RPMs)signal are required input to the ECU 86, any additional engine operatingparameters, such as temperature, can also be provided to the ECU formore sophisticated control of fueling and timing fluid pressure.Further, other types of electronically controlled valves could be usedin place of the rotary throttle valves. For example, solenoid valves,which are pulse width modulated to obtain the desired pressures couldreplace the rotary valves.

An accumulator 92 is provided in the timing fluid channel 78 to holdexcess amounts of timing fluid as needed. The timing fluid channel 78 isconnected to a timing fluid passage (not shown) in an injector 94 likethe timing fluid passage 38 in injector 10 in FIG. 1. Similarly, thefuel channel 80 is connected to a fuel supply passage (not shown) ininjector 94 that is like fuel passage 42 in FIG. 1. A fuel return line96 provides a fluid connection between the injector drain (not shown)and the fuel source 68.

The closed loop system shown and described with reference to FIG. 5provides the precise and independent pressure control of both fuel andtiming fluid desired for optimum functioning of a high pressureinjector. However, the use of pressure transducers 82, 84, which must becarefully inspected and usually changed often, could make this systemsomewhat costly. A less costly system that does not employ pressuretransducers is shown in FIG. 6.

The electronically controlled fuel supply system of FIG. 6 also employsa gear pump 102 in an open loop control system which sets fuel channeland timing channel pressures with an electronically actuated pressurecontroller arrangement. An electronic control unit 104 monitors theposition of the engine throttle 106, the output of exhaust gasrecirculator (EGR) 107, and the output of a plurality of sensors 108.The sensors 108 monitor engine operating parameters, such as enginespeed, temperature, emissions levels and the like, and provideinformation relating to these parameters to the electronic control unit104. Electronic control unit 104 processes this information andactivates an electronically controlled fuel supply valve 110. Fuelsupply valve 110 includes an electronic actuator 112 positioned againsta spring 114, which thus creates a known force acting against a plunger(not shown) in a flow divider 115 to achieve the desired pressure forthe engine operating conditions. The actuator 112 is driven by a motor116, which is preferably a stepping motor or a DC motor with positionfeedback capability that will assure the accuracy of the position ofactuator 112.

Fuel is fed to the flow divider 115 under pressure from the gear pump102 through fuel channel 103. Inside flow divider 115 the fuel flow isdivided into two channels: rail 118 and rail 120. The pressure of thefuel in rail 118 is set by the action of the flow divider 115 inresponse to the relative pressure request in rail 118. Likewise, thepressure of the fuel in rail 120 is set by controller 122 as will beexplained in greater detail later. If the pressure request in rail 120is higher than the pressure request in rail 118, the flow divider 115will throttle rail 118. If, on the other hand, the pressure request inrail 118 is higher than the pressure request in rail 120, the flowdivider 115 will throttle rail 120. The use of the flow divider 115allows a simpler fuel pump to be used with the type of circuit shown inFIG. 6, in part because the pressure in channel 103 is modulated so thatit never exceeds the maximum pressure requested in either rail 118 orrail 120. This differs from other fuel supply circuits that do notemploy a flow divider such as 115 in which the pressure in the fuelsupply channels and rails will always be the maximum preset value. Inthis manner the supply of fuel having a pressure which is optimum forthe particular engine operating conditions is provided to supply rails118 and 120.

Rail 118 is a fueling channel and is connected directly to a pluralityof high pressure fuel injectors like injector 10 in FIG. 1. Only onesuch injector, 119, is shown in FIG. 6. Rail 120 is the timing channelthat provides timing fluid in the form of fuel to the injectors. Thepressure of the fuel in rail 120 is adjusted by an electronicallyactuated timing pressure controller 122.

The timing pressure controller 122 is similar to the fuel supply valve110 in that it includes an electronic actuator 124 positioned against aspring 126 to create a known force acting against the area of a plungercounterbore 128, thereby creating a bypass pressure regulator whichimparts a known pressure to the timing fluid in rail sections 120 and132 downstream of the controller 122. Rail section 132 directly suppliestiming fluid to the injector 119. A motor 130, which can be a steppingmotor, a DC motor with position feedback or the like, drives actuator124 in a manner which assures that the position of actuator 124 isaccurately known. Actuator 124 is set against spring 126 in response tooutput from ECU 104. The electronic control unit receives input from thethrottle 106, EGR 107 and sensors 108 and, thus, is able to processinformation regarding all relevant engine operating parameters togenerate an output signal to timing pressure controller 122. This outputsignal directs the motor 130 to set the actuator 124 so that it willexert precisely the force required on plunger counterbore 128 to producethe timing fluid pressure in rail section 132 and, ultimately, ininjector 119 to create an hydraulic link of the length required toadvance timing in accordance with injection requirements. Under highspeed engine operation conditions, this timing fluid achieves injectorSAC pressures in excess of 30,000 psi.

FIG. 7 illustrates a third injector fuel and timing fluid supply systemembodiment. This embodiment could be employed with either a closed loopsystem, such as the system shown in FIG. 5, or with an open loop system,such as the system shown in FIG. 6. The system shown in FIG. 7 requiresonly a minimal amount of electrical energy to operate and, therefore,places less of a load on the electrical system. A gear pump 140 pumpsfuel from a reservoir 142 into a fuel supply channel 144. A pressureregulator 146 regulates the pressure of the fuel in supply channel 144as required before supply channel 144 bifurcates to form a fuelingchannel 148 and a timing fluid channel 150. In the FIG. 7 embodiment apulse width modulated solenoid pilot valve 152 is positioned on one sideof a servo valve 154 in section 156 of the fueling channel 148, and asimilar pulse width modulated solenoid pilot valve 158 is positioned onone side of a servo valve 160 in section 162 of the timing channel 150.Each of the solenoid valves is also connected to a drain line whichultimately provides a fluid connection between the valve and fuelreservoir 142. Drain line 153 allows fluid to flow from solenoid valve152 to reservoir 142, and drain line 159 allows fluid to flow fromsolenoid valve 158 to reservoir 142. The fuel in reservoir lines 153 and159 will have a lower pressure than the fuel in lines 156 and 162.Restricted orifices 164, 166 are positioned in channel sections 156 and162, respectively, to assist in maintaining the appropriate pressurelevels in these lines by restricting the flow of fuel past each of theservo valves.

Although pulse width modulated solenoid valves are shown in FIG. 7,rotary valves or any other similar types of valves that can beelectronically controlled could be used as pilot valves in this type ofsystem. The valves 152, 158 are actuated by an output signal from anelectronic control unit (not shown) similar to ECUs 86 and 104 in FIGS.5 and 6, respectively.

Information regarding engine operating conditions is used to provide anoutput signal to each of the valves 152 and 158 that will actuate eachvalve to set an appropriate pilot pressure on one side of each of theservo valves 154, 160. The servo valve 154 in fueling channel 148 willthen regulate the fuel flow until the pressure of the fuel flowing intofueling channel section 168 is equal to the pilot pressure. The fuel inchannel section 168 is then supplied at this pressure to a plurality ofinjector fuel passages, shown schematically at 170. The pressure of thefuel to be injected, therefore, is precisely controlled by the servovalve 154 in accordance with the pilot pressure set by the solenoidvalve 152.

Likewise, the servo valve in timing fluid channel 150 regulates the flowof timing fluid (fuel) into timing fluid channel section 172 so that thepressure of the timing fluid supplied to the injectors, shownschematically at 170, is equal to the pilot pressure set by the solenoidvalve 158. As previously discussed, this pressure is set in response tothe output of a variety of engine operating conditions supplied to anelectronic control unit (not shown) programmed to actuate the pilotvalve 158 to set the pilot pressure in accordance with the existingengine conditions. As these conditions change, different information issupplied to the electronic control unit so that an appropriate outputsignal can be generated to reset the pilot valve to change the pilotpressure as required. The control of the timing fluid pressure,therefore, is infinitely variable in response to engine operatingconditions. The pressure of the timing fluid can be infinitely varied inresponse to engine temperature, emissions levels, fuel pressure and anyother operating conditions so that fluid which actually enters theinjector has the pressure required to produce and sustain a hydrauliclink of a length which will advance timing of the fuel injected.Moreover, since the monitoring of engine operating conditions occursconstantly during engine operation, information required to determineproper timing fluid pressure is constantly processed by the electroniccontrol unit, and signals are constantly being directed to the pilotvalve to change the pilot pressure accordingly as required.

As previously noted, the pilot valve/servo valve arrangement could beemployed in either an open loop or a closed loop fuel and timing fluidsupply system. If an open loop arrangement is used, however, the use ofa pulse width modulated solenoid valve as the pilot valve would requiremore precise control than would the use of such a valve with a closedloop arrangement. The use of a pilot valve/servo valve combinationpresents additional advantages. Standard gasoline engine electronics maybe used on a diesel engine by employing standard gasoline injectorvalves as pilot valves in place of the solenoid valves shown in FIG. 7.Moreover, since the electronics required for this arrangement arerelatively low in cost, the use of a pilot valve/servo valve arrangementto control fuel and timing fluid pressures in a heavy duty engineachieves the precision of control required at a lower cost than othersystems available for such engines.

FIG. 8 illustrates yet another embodiment of a fuel and timing fluidsupply system which can be employed with high pressure fuel injectors.In this embodiment, a gear pump 180 draws fuel from a reservoir 182 anddirects it through a channel 184 past pressurizing valve 199 to acentral groove in the valve element 186 of a spool valve 187. Also gearpump 180 supplies fuel from upstream of pressurizing valve 199 throughpassage 185 to cavity 189 of valve assembly 187. Orifice 185' permitsthe pressure in passage 185 to be lower than the pressure in channel184. The spool valve 187 functions in the same manner as flow divider115 discussed above in connection with FIG. 6. A spring 188 mayoptionally be included in valve 187 to bias the valve element 186 to aposition which blocks the flow of fuel into fueling channel 190 whilepermitting the flow of timing fuel into timing channel 192. When thespring 188 is omitted, whether the fueling channel or the timing channelis open first will depend on the relative pressures at opposite ends ofthe valve element 187. An electronically actuated fueling control valve194 responsive to the output of an electronic control unit (not shown),such as described above in accordance with other embodiments of thepresent invention, regulates the fuel pressure in cavity 189 which isessentially the same as in fueling channel 190. The pressure of the fuelin channel 190, which is supplied directly to a plurality of injectors,shown schematically at 196, is controlled by control valve 194 inresponse to various engine operating conditions.

The valve 187 will throttle either fueling channel 190 or timing channel192 as required depending upon the relative pressure requests in eachchannel. If the pressure request in channel 190 is higher than thepressure request in channel 192, the valve 187 will throttle channel192. Conversely, channel 190 will be throttled by valve 187 if thepressure request in channel 192 is higher than the pressure request inchannel 190. Further, the pressure in channel 184 will never exceed themaximum pressure request of either channel 190 or channel 192, by morethan the setting of pressurizing valve 199 which is typically a lowpressure only sufficient to counteract the force of spring 188 if thepressure in both channels 190 and 192 is very low.

An electronically controlled timing control valve 198 is locatedadjacent to the timing fluid channel 192. The timing control valve 198bypasses fuel used for timing fluid through branch fuel channel 197which is connected to timing channel 192 and thus regulates the pressureof the timing fluid in channel 192 in response to the output of anelectronic control unit (not shown). As in the embodiments discussedabove, the electronic control unit receives information relating toengine operating conditions that would effect the timing of fuelinjection. An appropriate control signal is then provided to valve 198,actuating it to make any necessary adjustments in timing fluid flow intochannel 196 to insure that the pressure of the timing fluid will createa hydraulic link having a length sufficient to advance timing asrequired for the engine conditions. It can be seen from FIG. 8 that theflow of fuel into the timing channel 192 will be controlledsubstantially completely by the timing control valve 198.

FIG. 9 illustrates, schematically, an additional embodiment of a fuelsupply system which will satisfy the fuel and timing fluid requirementsof a high pressure fuel injector such as that shown in FIG. 1. In thisembodiment a gear pump 200 draws fuel through a supply channel 201 froma reservoir 202 and pumps it through a conduit 204 to a valve 206, whichis preferably a solenoid-type shut down valve. A relief valve 235prevents damage to pump 200 when valve 206 is closed and also regulatesthe maximum pressure available in passages 214 and 226. From valve 206,the fuel is directed to a fuel supply passage 208. The shut down valve206 can be adjusted to stop the flow of fuel to the fuel supply passage208 if necessary. Otherwise, the fuel supply passage directs fuel to apair of electronically controlled rotary actuators, such as steppingmotors, 210 and 212.

One of the rotary actuators 210 is located in the fuel channel 214 whichsupplies fuel to be injected to a plurality of injectors 216, only twoof which are shown in FIG. 9. The rotary actuator 210, which is thefueling actuator, includes a rotating throttle shaft 218 that rotates inthe direction of the arrow 220 to regulate fuel flow through a fuelthrottle valve 222. A pressure transducer 224 is located in the fuelingchannel 214 just downstream of the fuel throttle valve 222. The pressuretransducer 224 measures the pressure of the fuel in fuel channel 214 andthis information is provided to an electronic control unit (not shown)like those discussed above. The electronic control unit integrates andprocesses this information with that regarding various engine operatingconditions so that the movement of the throttle shaft can be adjusted asrequired to change the pressure of the fuel flowing through fuel channelor rail 214 to the injectors 216.

The second actuator 212 operates in a like manner to control thepressure of the fuel supplied to the timing channel 226. A throttleshaft 228 rotates in the direction of arrow 230 to control fuel flowfrom conduit 208 through the throttle valve 232 into timing channel 226.A pressure transducer 234 provides pressure measurements of the fuel inthe timing channel to the electronic control unit (not shown), which inturn, regulates the timing actuator 212, thus controlling the amount andconcomitantly the pressure of the timing fuel supplied to the injectors216. A drain line 236 is provided between each of the injectors 216 andthe reservoir 202.

Unlike the fuel supply and control systems previously available, thecomponents of the fuel supply and control system described herein arenot required to be mounted together in a single unit, but can be mountedseparately. For example, the gear pump could be mounted on the rear ofthe cylinder head where it can be driven directly by an overheadcamshaft. Actuators and pressure regulators can be mounted on the sideof the cylinder head. This arrangement eliminates the requirement forany fuel plumbing external to the engine head. The only fuel plumbingrequired for the various embodiments of the present invention is asuction line to the gear pump and a drain line back to the fuel tank.The remaining lines and channels are formed by fuel drillings in thecylinder head and gear pump. FIGS. 10, 11 and 12 illustrate one possiblemounting arrangement of the present fuel supply and control system on atwo cylinder engine. Although only the mounting for a two cylinder and,hence, a two injector engine is shown and described in detail, a similarmounting arrangement could be employed on an engine having four, six ormore cylinders. If the engine has more than two cylinders, this systemstill requires only two rotary actuators, one to control the fuelpressure and one to control the timing fluid pressure.

FIG. 10 illustrates, in top view, an engine cylinder head 240. The gearpump 200 and shut down valve 206 may be located at one end 242 of thecylinder head 240. The fuel supply conduit 204 containing a pressurerelief valve, shown in dashed lines in FIG. 10 directs fuel from thegear pump to the shut-down valve 206 and is formed in the head byinternal drillings. Likewise, the fuel supply passage 208, whichsupplies fuel to the rotary actuator operated valves 222, 232, is formedby a drilling located within the head to provide a fluid connectionbetween the shut down valve 206 and the rotary actuator operated valves222, 232. A drain line 244 is formed in the head for draining fuel fromeach of the valves. The direction of fuel flow in this Figure and theremaining Figures is shown by arrows.

FIG. 11 illustrates the cylinder head of FIG. 10 as it would appearviewed from the side. The fueling channel 214 extends from the throttlevalve driven by actuator 210 to fuel port 252 for one injector and port254 for a second injector. The timing channel 226 and the drain line 236from the injectors, all shown in dashed lines in FIG. 11, are formed bydrilling the interior of the cylinder head. Timing fluid is supplied tochannel 226 from the throttle valve driven by actuator 212 by means ofvertical channel 246. Timing fluid ports 248 and 250 facilitate fluidconnection between the timing channel 226 and the corresponding fuelinjector bores (FIG. 12). Fuel ports 252 and 254 in like mannerfacilitate fluid connection between the fuel channel 214 and theinjector bores. The fuel exiting channel 236 is returned to the fuelsource through lines not illustrated in this Figure.

FIG. 12 illustrates, in cross-sectional view taken along line 12--12 inFIG. 11, the end of the cylinder head 256 opposite the end of the head242 on which the gear pump 200 is located. A single fuel injector bore258 and its attendant fuel and timing fluid connections is shown. Asubstantially identical bore will be provided for each injector. It willbe noted from FIG. 12 that the actuator 210 and throttle valve 222 arelocated adjacent to the injector bore 258. The other actuator 212 willalso be adjacent to a cylinder bore (not shown). This is the casebecause the engine shown has only two injectors. When the present systemis installed on an engine with more than two injectors, the two steppingmotors and throttle valves required may be positioned adjacent to one ofthe injector bores or in any other convenient location on the cylinderhead upstream of the injector bores.

The foregoing injector fuel supply mounting arrangement allows systemcomponents to be positioned on the cylinder head in locations spaced toobtain maximum use of internally drilled fluid channels. The specificconfiguration discussed is intended to be merely illustrative of onepossible mounting arrangement for the present high pressure injectorfuel supply system.

Industrial Applicability

The electronically controlled fuel supply system of the presentinvention will find its primary application in an internal combustionengine employing high pressure fuel injectors wherein SAC pressures inexcess of 30,000 psi are achieved. However, the present fuel supplysystem will also be useful in any internal combustion engine whereinextremely precise control of fueling and injection timing at relativelylow cost is a desired objective.

We claim:
 1. An electronically controlled fuel supply system forsupplying fuel and timing fluid to a plurality of fuel injectors in aninternal combustion engine, wherein each of said injectors includes ahydraulic link formed by said timing fluid which cooperates with aserially arranged plunger assembly to pressurize the fuel to be injectedwherein said hydraulic link may have a variable effective length inresponse to variations in pressure of said timing fluid supplied to thesaid injector, said fuel supply system comprising:(a) pump meansfluidically connected to a fuel reservoir for pumping fuel from thereservoir to fuel channel means for supplying fuel to the injectors andto timing fluid channel means separate from said fuel channel means forsupplying timing fluid to the injectors at a sufficient flow rate andpressure to operate the system; (b) electronically controlled fuelpressure regulating means fluidically connected to said pump means andto said injectors for regulating the pressure of the fuel to be suppliedthrough said fuel channel means to the injectors for controlling thequantity of fuel to be injected by said injector; (c) electronicallycontrolled timing fluid pressure regulating means fluidically separatedform said fuel pressure regulating means but fluidically connected tosaid pump means and to said injectors for regulating the pressure of thetiming fluid to be supplied through said timing channel means to theinjectors for controlling the quantity of timing fluid supplied to saidinjector to vary the length of said hydraulic link; and (d) electroniccontrol means for receiving and processing information relating to aplurality of engine operating conditions wherein said electronic controlmeans provides a first control signal to said fuel pressure regulatingmeans to actuate said fuel pressure regulating means to adjust thepressure of the fuel supplied tot he injectors to control thereby thequantity of fuel injected during each cycle of injection and a secondcontrol signal to said timing fluid pressure regulating means to adjustthe pressure of the timing fluid supplied to the injectors in responseto said engine operating conditions to a pressure sufficient to form ahydraulic link in said injector that will cause the time of injectionduring each cycle to vary in dependence on engine conditions.
 2. Thefuel supply system described in claim 1, wherein said fuel pressureregulating means is located in a first fluid channel between said pumpmeans and said injectors and said timing fluid pressure regulating meansis located in a second fluid channel separate from said first fluidchannel, said second fluid channel being fluidically connected to saidpump means, said first fluid channel and said injectors.
 3. The fuelsupply system described in claim 2, wherein said fuel pressureregulating means includes pressure transducer means for measuring thepressure of the fuel in said first channel and providing said fuelpressure measurement to said electronic control unit means and throttlevalve means for modulating the flow of fuel through said first channelto adjust the pressure thereof in response to an output signal from saidelectronic control unit means; and said timing fluid pressure regulatingmeans includes pressure transducer means for measuring the pressure ofthe timing fluid in said second channel and providing said timing fluidpressure measurement to said electronic control unit means and throttlevalve means for modulating the flow of timing fluid through said secondchannel.
 4. The fuel supply system described in claim 3, furtherincluding accumulator means located in said second channel between saidtiming fluid pressure regulating means and said injectors for holdingexcess timing fluid.
 5. The fuel supply system described in claim 2,wherein said fuel pressure regulating means and said timing fluidpressure regulating means each comprises a spring loaded electronicallyactuated assembly, wherein the pressure of each said spring is set byactuator means in response to a signal from said electronic control unitmeans indicative of engine operating conditions and further includesflow divider means for regulating the pressures of said fuel and saidtiming fluid relative to their respective pressure requests.
 6. The fuelsupply system described in claim 2, wherein said fuel pressureregulating means comprises a first pilot valve means for imparting afirst pilot pressure to said fuel in response to a signal from saidelectronic control means indicative of engine operating conditions and afirst servo valve means for imparting a pressure equal to said firstpilot pressure to the fuel in said fuel channel; and said timing fluidpressure regulating means comprises a second pilot valve means forimparting a second pilot pressure to said fuel in response to a signalfrom said electronic control means indicative of engine operatingconditions and a second servo valve means for imparting a pressure equalto said second pilot pressure to the timing fluid in said timing fluidchannel.
 7. The fuel supply system described in claim 2, wherein saidfuel pressure regulating means comprises a pilot valve means forimparting a pilot pressure to said fuel in response to a signal fromsaid electronic control means indicative of engine operating conditionsand a servo valve means for imparting a pressure equal to said pilotpressure to said fuel in said timing fluid channel and said injector. 8.The fuel supply system described in claim 7, further including valvemeans fluidically interposed between said fuel pressure regulating meansand said injectors for further modulating the pressure of said fuel andsaid timing fluid.
 9. An electronically controlled fuel supply systemfor supplying fuel and timing fluid to a plurality of fuel injectorslocated in a plurality of bores formed within the cylinder head of aninternal combustion engine, said fuel supply system comprising:(a) pumpmeans located at one end of said cylinder head for directing fuel to afuel supply channel contained entirely internally within said cylinderhead; (b) electronically controlled fuel pressure regulating meansfluidically interposed between said fuel supply channel and an injectorfuel rail contained entirely internally within said cylinder head forsupplying pressure modulated fuel to said plurality of injectors forcontrolling the quantity of fuel to be injected by said injector,wherein said injector fuel rail is fluidically connected to each of saidplurality of bores; (c) electronically controlled timing fluid pressureregulating means fluidically separated from said fuel pressureregulating means and fluidically interposed between said fuel supplychannel and a timing channel contained entirely internally within saidcylinder head for supplying pressure modulated timing fluid to saidplurality of injectors for controlling the quantity of said timing fluidsupplied to said injectors, wherein said timing channel is fluidicallyconnected to each of said plurality of bores; and (d) electronic controlmeans for receiving and processing information relating to a pluralityof engine operating conditions, wherein said electronic control meansprovides signals to said fuel pressure regulating means to actuate saidfuel pressure regulating means to cause said injectors to inject avarying quantity of fuel during each injector cycle depending on engineconditions and provides signals to said timing fluid pressure regulatingmeans to adjust the pressure of the timing fluid int he timing channelto deliver timing fluid to each of said injectors to create a hydrauliclink of a length that will cause the time of injection during each cycleto vary in dependence on engine conditions.
 10. The fuel supply systemdescribed in claim 9, further including shut down valve means mounted onthe same end of the cylinder head as said pump means and fluidicallyconnected to said pump means and to said fuel supply channel forshutting off the flow of fuel to said fuel rail and said timing channel.11. The fuel supply system described in claim 10, wherein said fuelpressure regulating means and said timing fluid pressure regulatingmeans each comprises a throttle valve activated by a rotary actuator.12. The fuel supply system described in claim 9, wherein said fuelpressure regulating means and said timing fluid pressure regulatingmeans each comprises a pilot valve means for imparting a pilot pressureto said fuel in response to output from said electronic control meansindicative of engine operating conditions and a servo valve means forimparting a pressure equal to said pilot pressure to said fuel in saidfuel rail and to said timing fluid in said timing fluid channel.
 13. Thefuel supply system described in claim 10, wherein said fuel pressureregulating means and said timing fluid pressure regulating means eachcomprises a spring loaded electronically actuated assembly, wherein thepressure of each said spring is set by actuator means in response to asignal from said electronic control unit means indicative of engineoperating conditions and the pressure of each said spring determines thepressure of, respectively, said fuel and said timing fluid.